The present invention refers to an improved apparatus for manufacturing air filters for motor vehicles, such as air filters for the engine or the passenger compartment of a motor vehicle.
An air filter for automotive use is usually composed of a filtering element made of pleated paper, shaped as a parallelepiped or a cylinder, to which a peripheral rim or border is sticked, made of foamed resin, usually polyurethane (PU) or polyvinylchloride (PVC). The foamed resin is generally in the form of a flexible foam member that fixes shape and dimensions of the filtering element, at the same time acting as a seal gasket when the filter is assembled in its housing, on board of the vehicle.
The foamed resin rim is usually obtained by placing into a die the properly pleated paper, and then injecting or casting the resin into a die cavity or recess extending all around the paper. The plastic melted resin sticks to the paper forming a border or rim that copies the die cavity shape.
EP-A-0 486 846 according to which the preamble of claim 1 has been drafted discloses an apparatus for manufacturing an air filter for motor vehicles which solves the problems deriving from a possible not uniform distribution of the resin along the die cavity, and an excessive penetration of the resin into the filtering paper, by providing a channel defined in the lower die and cooperating with a movable frame for realizing a resin injection cavity and a resin expansion cavity.
However the apparatus disclosed by this patent has the drawback according to which the gasket 3 provided between the upper and the lower dies may not be capable of forming a sufficient seal to the expanding resin which therefore could enter the space or gap between the upper die 2 and the movable frame 10, thus hindering the slide movement of the movable frame 10 and in case blocking the whole apparatus.
Therefore the object of the present invention is to solve such sealing problem of the known apparatus in respect of resin leaks to regions where it has not to enter: this object is achieved through an improved construction of the apparatus upper die that allows for using the resin itself as a sealing gasket.